The use of blow-molding as a method for manufacturing various sorts of articles is generally well known. Typically, this process involves the use of a mold consisting of two separate halves or portions having cavities of particularly desired shapes and sizes. Usually, one extrudes a large-diameter, sealed tube of molten material (commonly referred to as a “parison”), places the tube between the mold halves, and closes the mold around the tube. Fluid pressure is then introduced into the tube, forcing the molten tube against the walls of the cavities, conforming the tube to the shape thereof. The pressure is maintained until the molten material cools and solidifies. The pressure is then released, the mold halves are pulled apart, and the hardened article is ejected therefrom.
One such article that is commonly manufactured in this manner is double wall cases. By producing cases in this manner, one is able to produce a device that is capable of carrying and protecting tools placed inside the case that has a multitude of desirable physical characteristics—such as rigidity, scuff resistance, and impact absorption—yet that is relatively inexpensive to manufacture. In some instances, these cases are formed as single-piece cases using the process described above, where one mold half forms the exterior of both the base and lid portions of the case, while the other mold half forms the interior of both base and lid portions. Usually, the mold half forming the exterior of the case forms a wall with a smooth, attractive shape, while the mold half that forms the interior of the case is often molded with compartments to hold specific contents. In other instances, the process described above can be used to separately create the base and lid portions of the case, which can subsequently be connected together.
Though such cases are generally well known in the art, efforts have been made to increase the carrying capacity of such cases while reducing the size of the case, as attempts to increase the interior space of the case can quickly increase the weight and size of the case due to its double wall nature. Accordingly, it has been suggested to cut out sections of the interior walls of the case in order to utilize the wasted volume of space between the double walls. By doing so, the case can be made smaller in light of the fact that this previously unused space is now being used to house the objects being carried in the case. Moreover, by removing sections of the walls, the case also decreases significantly in weight.
For example, U.S. Pat. Nos. 3,317,955 and 3,327,841 to Schurman, et al., disclose cases in which a portion of the case wall is cut out after blow-molding. Specifically, the '955 patent, which discloses the earliest known double wall case blow-molded case, illustrates a rectangular cutout of most of the inside wall of the base portion. Similarly, the '841 patent discloses a partial cutout shaped to accommodate the outline of a pistol-type soldering gun, where the gun is further supported by a cradle molded in the outside wall of the base portion of the case, while the space under the uncut portion of the inside base is usable for storage of an electric cord, thereby facilitating the use of what was previously wasted, unused space. In these particular examples, because the blow molding process involves the use of a parison with a continuous, unbroken surface (and thus, the mold itself cannot produce any holes in the blow-molded wall other than the hole or holes through which the fluid pressure is introduced), a section of the case wall is cut or burned after the blow molding process is completed and the case has been ejected from the mold. For example, cutting the inner wall was often accomplished with the use of a small circular saw blade mounted to a router and guided by a molded vertical lip surrounding the area to be cut. The router was fixed and the case was moved around the router axis by hand or by mechanical means. Round holes were often cut with hole saws, or occasionally, were burned.
Another, more improved method of removing a section of the inner wall of the case is to punch a hole in this wall during the blow molding process. Examples of such methods are disclosed in U.S. patent application Ser. Nos. 10/958,824 and 11/105,721, each of which is assigned to the assignee of the present application and are incorporated herein by reference. In these varieties, punches are used during the blow-molding process to produce the desired holes. The punch, when in an unactivated position, forms a portion of mold surface, against which the walls of the blow molded case are blown. Then, at a predetermined interval, before the walls of the case are fully hardened, the punch is moved to an activated position, creating a hole in the wall of the case.
One limitation such cases may still have in some applications, however, is their ability to accommodate compartments for accessories. For example, one common use for such cases is tools, such as a drill, which, in addition to the main tool, include other accessories, such as drill bits. However, when a hole is created in an inner case wall, a fair amount of the remaining portions of the wall may be required to provide support for the perimeter of the hole, which retains the main tool. Accordingly, the available space for additional holes in this inner wall for accommodating accessories is sometimes limited.
What is desired, therefore, is a blow molded case for housing an object as well as accessories of the object. What is further desired is a blow molded case that has a high carry capacity, yet is not heavy or cumbersome. What is also desired is a blow molded case that is easy and inexpensive to manufacture, does not produce residual sawdust and/or charred plastic, and does not require a long blow molding cycle.